A LECTURE ON MAGNETISM. 363 



the reciprocity of this action by removing- the suspended 

 needle, and putting the other in its place. You obtain the 

 same result. The attraction, then, is mutual, and the re 

 pulsion is mutual, and you have thus demonstrated in the 

 clearest manner the fundamental law of magnetism, that 

 like poles repel, and that unlike poles attract each other. 

 You may say that this is all easily understood without do 

 ing ; but do it, and your knowledge will not be confined to 

 what I have uttered here. 



I have said that one end of your magnet has a mark 

 upon it ; lay several silk fibres together, so as to get suffi 

 cient strength, or employ a thin silk ribbon, and form a loop 

 large enough to hold your magnet. Suspend it ; it turns 

 its marked end toward the north. This marked end is that 

 which in England is called the north pole. If a common 

 smith has made your magnet, it will be convenient to deter- 

 mine its north pole yourself, and to mark it with a file. 

 You vary your experiments by causing your magnetized 

 darning-needle to attract and repel your large magnet ; it 

 is quite competent to do so. In magnetizing the needle, I 

 have supposed the eye-end to be the last to quit the marked 

 end of the magnet ; that end of the needle is a south pole. 

 The end which last quits the magnet is always opposed in 

 polarity to the end of the magnet with which it has been in 

 contact. Brought near each other they mutually attract, 

 and thus demonstrate that they are unlike poles. 



You may perhaps learn all this in a single hour ; but 

 spend several at it, if necessary; and remember, under 

 standing it is not sufficient: you must obtain a manual 

 aptitude in addressing Nature. If you speak to your fellow- 

 man, you are not entitled to use jargon. Bad experiments 

 are jargon addressed to Nature, and just as much to be dep 

 recated. A manual dexterity in illustrating the interaction 

 of magnetic poles is of the utmost importance at this stage 

 of your progress, and you must not neglect attaining this 



